1.Excessive love or admiration of oneself.
2.A psychological condition characterized by self-preoccupation, lack of empathy, and unconscious deficits in self-esteem.
3.Erotic pleasure derived from contemplation or admiration of one's own body or self, especially as a fixation on or a regression to an infantile stage of development.

A narcissist is someone who suffers from a narcessistic personality dissorder. A narcissist is always right and has the urge to make you feel less than him/her.
Medical Definition of Narcissism:
Narcissism is the pattern of traits and behaviors which involve infatuation and obsession with one's self to the exclusion of others and the egotistic and ruthless pursuit of one's gratification, dominance and ambition. In everyday use outside the field of psychology, the word generally refers to people who just are inordinately fond of themselves, without the pathological connotations.

Unlike the general idea that narcissism is bad. It's actualy rather good. You never pay any attention to what others say about you nor care about it. You think yourself to be better looking and smarter than others, wich is handy in alot of situations.
Narcissist's are realy common and you can find them in every corner of the world. You probely one of them yourself.

Taken from the ancient Greek character who fell in love with his own reflection.

Somebody who is completely in love with himself/herself and most likely is intensely turned on by their relection. Somebody who is too vain and self-absorbed to notice other people.

I would not be the least bit surprised if Narcissus were from the United States; self-aborbed, self-important, jingoistic, bewildered at the thought that there are others in the world besides us... the U.S. seems to be the perfect breeding ground for narcissists.